The present invention relates to the field of overfill protection devices or filling limitors for liquid storage tanks and, more particularly, to devices of the foregoing type that are especially suited for shallow tanks such as those known as xe2x80x9cgenerator day tanksxe2x80x9d used to store fuel for backup generators at hospitals and the like, or those found in or around homes to hold fuel oil for home heating.
Day tanks and home fuel oil tanks and the like are typically refilled by supply trucks that travel to the site and connect a hose from the truck to an inlet tube on the top wall of the tank. The hose is connected to the inlet tube in a sealed manner, and a pump on the truck delivers the fuel through the hose and into the tank under pressure. The tank typically has a vent that allows air to escape as the liquid level within the tank rises. Thus, although the supply line from the trunk to the tank is a sealed path, it is possible that the tank can become overfilled to such an extent that fuel spills out through the vent if the operator is not particularly attentive or if automatic shut-off mechanism at the truck fails to function properly.
Accordingly, there is a need for a way of shutting off additional inflow of fuel to the tank to prevent accidental overfilling and spillage, notwithstanding the presence of other shut-off mechanisms associated with the supply apparatus. While various types of electro-mechanical devices of this type are currently available, they suffer from numerous disadvantages, including cost and complexity.
The present invention provides a filling limitor or overfill protection device that is relatively simple, yet highly effective. It can be readily retro-fitted to existing tanks and is safe and reliable in operation. It is particularly well suited for shallow tanks in which the distance between the top and bottom walls of the tank is relative short, for example three feet or less. Although disposed within the flow path of incoming liquid, the valve of the device is capable of successfully resisting any tendency for the pressurized liquid to close the valve prematurely, which would result in only partial filling of the tank.
In one preferred embodiment of the present invention a poppet valve is housed within a tubular valve body and is moveable axially between open and closed positions by an external float that is operably coupled with the valve. Although the poppet is located within the tubular valve body that defines the flow path, the poppet is protected from direct engagement with the incoming pressurized liquid by an overhead deflector that is axially aligned with the poppet. Fluid that would otherwise engage the poppet and force it down against its seat to prematurely close the port through the valve body is instead diverted out radially upon engagement with the deflector so as to enter an annular region around the deflector and pass to and through the port without impinging the poppet. Consequently, the poppet is only shifted to its closed position when the float intentionally moves it to such position in response to the liquid within the tank reaching a predetermined level.
In a preferred embodiment the limitor comprises an assembly having as its two main components a mounting tube that is adapted to be threadably attached to the top wall of the tank and a valve subassembly that is threadably attached to the mounting tube. The subassembly comprises a cylinder having an annular, externally threaded boss at its upper end that is threadably received by the internally threaded lower end of the mounting tube. The cylinder defines an inlet port which is opened and closed by a poppet operating above the port along an axial path of travel relative thereto. The poppet has a valve stem associated therewith projecting above and below the poppet so as to be guided in its reciprocal travel by upper and lower guide structure supported by the cylinder. The upper guide structure serves also as a deflector overlying the poppet to divert liquid flow away from the poppet. At its lower end, the valve stem is mechanically coupled with an operating arm of the float which is supported laterally outside of the cylinder, such arm being swingable up and down by the rising and falling level of liquid within the tank to correspondingly manipulate the valve stem.
Various alternative embodiments are disclosed, including embodiments that utilize a drop tube extending down from the valve body for use in tanks that are not as shallow or where the incoming liquid is preferably delivered close to the bottom of the tank to avoid splashing or turbulence. The drop tube embodiments contemplate the provision of an opening in a sidewall of the drop tube that is sized to accept the float when the float is swung down and moved into the opening to present a slender profile for inserting the assembly through the hole in the top wall of the tank during installation. The opening in the sidewall is covered by an internally disposed cover that is spring biased toward the opening yet can be yieldably pushed into the interior of the drop tube by the float as the float enters the opening from outside the drop tube. The float arm is so designed in such embodiments that it can resiliently flex to a position permitting the float to be swung beyond its normal limit of travel into the inside of the drop tube, or the arm is of two-part, spring loaded construction to provide the desired amount of relief to permit the movement of the float to its installation position.